Conformations of substituted benzophenones

Abstract

The inclination of the two aryl rings (ring twists) in a series of benzophenone molecules has been examined. For each structure the dihedral angle (between the planes of the two sets of six aromatic C atoms) relates to both the steric considerations of the single molecule and the packing forces related to the crystal structure. Six new benzophenone structures are incorporated into the study including 2,2′-dihydroxy-4,4′-dimethoxybenzophenone (I), C15H14O5, that appears to have the smallest reported twist angle, 37.85 (5)°, of any substituted benzophenone reported to date. Three further benzophenones, 4,4′-bis(diethylamino)benzophenone (II), C21H28N2O, 3,4-dihydroxybenzophenone (III), C13H10O3, and 3-hydroxybenzophenone (IV), C13H10O2, have similar ring twists [49.83 (5), 49.84 (5) and 51.61 (5)°, respectively] that are comparable with the value of 54° found for the orthorhombic form of unsubstituted benzophenone. 4-Chloro-4′-hydroxybenzophenone (V), C13H9ClO2, has a ring twist of 64.66 (8)° that is close to the value of 65° found in the metastable monoclinic form of unsubstituted benzophenone and 2-amino-2′,5-dichlorobenzophenone (VI), C13H9Cl2NO2, has a large ring twist of 83.72 (6)°. Comparisons with a further 98 substituted benzophenone molecules from the Cambridge Structural Database (CSD) have been made.